Wireless communications operating according to a predetermined protocol have gained worldwide popularity. The advantages of the wireless medium include the capacity to address broad geographic areas without expensive infrastructure development such as running cables. The broadband wireless access industry often is guided by IEEE standard 802.16 for wide area networks.
Worldwide Interoperability for Microwave Access (WiMAX) is a wireless communications technology for providing wireless data based on the IEEE standard 802.16. A WIMAX network provides an alternative to cabled access networks, such as a digital subscriber line (DSL). In addition, the WiMAX technology may provide fixed, nomadic, portable, and mobile wireless broadband connectivity to a base station.
The IEEE standard 802.16 supports a multicast and broadcast service (MBS), which can provide service data to a plurality of users who desire to receive the same service in the WiMAX network. For example, the service data may be movies, games, or TV programs, and is usually stored on one or more MBS servers. A mobile station (MS), such as a mobile phone or a laptop computer, subscribing to an MBS may receive data relating to the MBS through access to one or more base stations (BSs) in the WiMAX network.
Typically, MBS data is transmitted in data frames from the BS to the MS. For example, according to the IEEE standard 802.16, a data frame may include a downlink map (DL-MAP), an MBS map (MBS-MAP), a plurality of MBS data bursts including content of MBSs delivered by the BS, and other information. The DL-MAP includes an MBS-MAP information element (MBS-MAP-IE), which indicates in the data frame a location of the MBS-MAP based on, e.g., symbol offsets, and provides information for the MS to perform synchronization with the MBS-MAP. In other words, based on the MBS-MAP-IE, the MS may know when to read the MBS-MAP.
The MBS-MAP includes one or more MBS data information elements (MBS-DATA-IEs) or extended MBS data information elements (Extended MBS-DATA-IEs), collectively referred to herein as MBS-DATA-IEs, which provide access information for MBS data bursts in the data frames. For example, MBS data is typically transmitted on a plurality of logical channels of the MBS, and each of the MBS-DATA-IEs provides a connection identifier for one of the plurality of logical channels. Also for example, a first one of the MBS-DATA-IEs indicates in the data frames a location of an MBS data burst corresponding to a first one of the logical channels based on, e.g., frame and symbol offsets. The first one of the MBS-DATA-IEs also indicates in the data frames a location of a next MBS-MAP including information relating to the first one of the logical channels. Based on the first one of the MBS-DATA-IEs, the MS may know when to read the MBS data burst corresponding to the first one of the logical channels, and know when to read the next MBS-MAP including the information regarding the first one of the logical channels.
FIG. 1 illustrates a conventional MBS data structure 100, according to the IEEE standard 802.16. The MBS data structure 100 includes a plurality of data frames 101 transmitted by the BS. For example, the BS may deliver content of a first TV program on the first one of the logical channels, content of a second TV program on a second one of the logical channels, and content of a movie on a third one of the logical channels. For convenience of illustration, only MBS-MAP-IEs, MBS-MAPs, MBS-DATA-IEs, and MBS data bursts that relate to the first, second, and third logical channels are labeled on the MBS data structure 100 in FIG. 1.
Referring to FIG. 1, the MBS data structure 100 includes MBS-MAP-IEs 102, 104, 106, MBS-MAPs 112, 114, 116, and a plurality of data bursts 122-i (i=1, 2, 3), 124-i (i=1, 2), 126-i (i=1, 2, 3). The MBS-MAPs 112, 114, 116 further include MBS-DATA-IEs 112-i (i=1, 2, 3), 114-i (i=1, 2), and 116-i (i=1, 2, 3), respectively. The MBS-DATA-IEs 112-1, 114-1, 116-1 and the MBS data bursts 122-1, 124-1, 126-1 relate to the first logical channel. The MBS-DATA-IEs 112-2, 114-2, 116-2 and the MBS data bursts 122-2, 124-2, 126-2 relate to the second logical channel. The MBS-DATA-IEs 112-3, 116-3 and the MBS data bursts 122-3, 126-3 relate to the third logical channel.
The MBS-MAP-IEs 102, 104, and 106 indicate locations of the MBS-MAPs 112, 114, and 116 in the data frames 101, respectively, which is illustrated by the dashed arrows in FIG. 1. Based on the MBS-MAP-IE 102, the MS may know when to read the MBS-MAP 112. Based on the MBS-MAP-IE 104, the MS may know when to read the MBS-MAP 114. Based on the MBS-MAP-IE 106, the MS may know when to read the MBS-MAP 116.
The MBS-DATA-IEs 112-1, 114-1, and 116-1 provide for the first logical channel a connection identifier, and indicate in the data frames 101 locations of the MBS data bursts 122-1, 124-1, and 126-1, respectively. In addition, the MBS-DATA-IE 112-1 in the MBS-MAP 112 indicates in the data frames 101 a location of the next MBS-MAP 114 including the MBS-DATA-IE 114-1. The MBS-DATA-IE 114-1 further indicates a location of the next MBS-MAP 116 including the MBS-DATA-IE 116-1. These indications are also illustrated by the dashed arrows in FIG. 1.
The MS may acquire MBS-MAP synchronization, i.e., locate in the data frames 101 an MBS-MAP that includes information relating to one of the logical channels on which desired content is delivered, by reading MBS-MAP-IEs in the data frames 101. For example, if the MS wants to receive the content on the first logical channel, the MS may know when to read the MBS-MAP 112 based on the MBS-MAP-IE 102. Based on the MBS-DATA-IE 112-1 in the MBS-MAP 112, the MS may know when to read the MBS data burst 122-1 and the next MBS-MAP 114 including the MBS-DATA-IE 114-1. Similarly, based on the MBS-DATA-IE 114-1, the MS may further know when to read the MBS data burst 124-1 and the next MBS-MAP 116 including the MBS-DATA-IE 116-1. In this way, the MS may read the MBS data bursts 122-1, 124-1, 126-1, which include the content delivered on the first logical channel. Similarly, the MS may read the MBS data bursts 122-2, 124-2, 126-2, which include the content delivered on the second logical channel, or the MBS data bursts 122-3, 126-3, which include the content delivered on the third logical channel.
In reality, the MS may miss the MBS-MAP 112 in the data frames 101 transmitted by the BS. For example, the MS that wants to receive the content delivered on the first logical channel may initially establish connection to the BS at a time after the MBS-MAP-IE 102 is transmitted. Also for example, the MS may switch to the first logical channel from another logical channel at a time after the MBS-MAP-IE 102 is transmitted. As a result, the MS needs to wait for a next MBS-MAP relating to the first channel, i.e., the MBS-MAP 114, to acquire MBS-MAP synchronization. Based on the MBS-DATA-IE 114-1 in the MBS-MAP 114, the MS may further read the MBS data burst 124-1 and following MBS data bursts.
As a result, power is consumed when the MS searches for the MBS-DATA-IE 114-1 in the data frames 101. A relatively long period of MBS-MAP synchronization in the MS may result in relatively high power consumption. For example, according to the IEEE standard 802.16, the MBS-MAP 114 could be transmitted several frames later than the MBS-MAP 112.